FORMULATION, CHARACTERIZATION AND COMPARATIVE EFFICACY STUDIES OF HYDROPHILIC AND LIPOPHILIC ASCORBIC ACID DERIVATIVES IN TOPICAL MULTIPLE EMULSIONS

Abstract

Ascorbic acid (vitamin C) and its derivatives, mainly due to their antioxidant properties, are gaining popularity as ingredients in cosmetic formulations because they can protect the skin against exogenous and endogenous harmful agents, and have gained considerable interest in the treatment of various skin conditions including hyperpigmentation, acne, inflammation, dry skin and aging. The current work aimed to formulate and stabilize a carrier system in the form of topical water-in-oil-in-water (W/OW) emulsion; containing various combinations of ascorbic acid derivatives (ascorbyl palmitate and sodium ascorbyl phosphate) to attain synergistic effects; with comparable antioxidant properties, their in- vitro characterization and in-vivo study on human volunteers. Stable control formulation (C 20 ) without active and stable antioxidant active formulations (ME 1 , ME 2 and ME 3 ) with vitamin C derivatives; ascorbyl palmitate + sodium ascorbyl phosphate of water-in-oil-in-water type were developed. Antioxidant activities of vitamin C derivatives as well as formulations containing these derivatives were determined by DPPH (2, 2-di-phenyl-1-picrylhydrazyl) assay. In-vitro characterization was based to investigate the changes in the physical stability (color, liquefaction, pH, conductivity, centrifugation, viscosity and rheological parameters) in active formulations (ME 1 , ME 2 and ME 3 ) containing vitamin C derivatives and control C 20 when placed to different storage conditions, i.e. 8oC, 25 oC, 40oC and 40 o C + 75% RH for a period of 90 days as per stability study guidelines. In-vivo characterization was based to investigate the effects of active formulations (ME 1 , ME 2 and ME 3 ) on various skin parameters like melanin, erythema, moisture contents, elasticity, sebum and surface evaluation of living skin (SELS parameters) on human female’s facial skin for an investigation period of 12 weeks. The study was single blinded, controlled, split face with 3-groups (ME 1 , ME 2 and ME 3 ) having 11 volunteers each. Statistical tools of ANOVA test and paired sample t-test were used to evaluate the changes produced. IXAntioxidant activities of ascorbyl palmitate, sodium ascorbyl phosphate and ascorbyl palmitate + sodium ascorbyl phosphate (combined) were 88%, 21%, 89% respectively. The fresh active formulations (ME 1 , ME 2 and ME 3 ) containing these derivatives showed 78%, 87% and 79% anti-oxidant activities, respectively. Active formulations containing ascorbic acid derivatives (0.5% each) as well as respective control C 20 showed good stability, pH, conductivity and rheology as desired, for 90 days in-vitro study period. Active formulations ME 1 , ME 2 and ME 3 showed significant changes and respective control (C 20 ) showed an insignificant decrease in skin melanin, erythema content, and sebum while an increase in skin hydration. Active formulation ME 1 showed significant effects on SELS i.e. SEr (skin roughness), SEsc (skin scaliness), SEsm (skin smoothness), SEw (skin wrinkles) parameters in comparison to control (C 20 ). SELS (SEr, SEsc, and SEw) parameters showed significant decline while SEsm (Skin smoothness) showed a significant increase after topical application of ME 2 and ME 3 in comparison to respective control (C 20 ).